It is well recognised that dental plaque is a major causative agent of caries and periodontal disease. Broadly, plaque consists of an adhesive mass of bacteria, mucins, food and other organic matter which if present for long enough on the teeth, calcifies to form calculus. Consequently, it is appreciated that the effective and complete removal of plaque is essential to the maintenance of good oral hygiene.
Unfortunately, the achievement of the goal of the removal of substantially all plaque from the oral tissues on a regular basis is not achievable by the vast majority of people, even when the individual recognises the need for plaque removal. It is therefore not unexpected that the WHO have stated that dental disease is the most common of all diseases affecting man throughout the world today.
The removal of plaque from the oral tissues at an early stage of its development may be achieved by brushing. However, if calcification occurs, then the resultant calculus may only be removed by vigorous mechanical action, usually performed by a dentist. It is therefore important to ensure plaque removal before calcification occurs.
One difficulty in ensuring that plaque is removed at an early stage is that an individual cannot readily either visually or otherwise determine if all plaque has been removed. To overcome this difficulty, the use of plaque disclosing compositions have been previously suggested. Such compositions usually consist of a dye that only stains the plaque thereby allowing its visualisation in contrast to other parts of the oral cavity.
In the prior art, these disclosing compositions have been presented in a variety of forms including rinses, lozenges, wafers and chewable tablets. It is to be noted that all of these compositions are used either before or more usually, after brushing. When used after brushing it would be expected that the composition would reveal plaque to be removed by rebrushing.
Whilst this approach has potential for the effective control of plaque, in fact the individual rarely continues the use of such disclosing composition as it requires an additional step over the normal routine of merely brushing the teeth with a dentrifice.
It is this extra step, a complicated procedure of intentional application that compromises convenience to the point where it is often abandoned or rarely maintained as a routine procedure by most people.
In Australian Patent Application 46357/79, it is taught that a disclosing agent may be included in a suitable dentrifice paste. Disclosing compositions containing mixtures of dye that result in the plaque being disclosed as a green colour are described. Such a composition would appear to meet the need for a plaque disclosing composition that is capable of being included in the normal toothbrushing routine.
It has, however, been recognized that it is important to be able to distinguish between recently formed plaque and "old" plaque. The reason for this is that "old" plaque has been found to be a causative agent of periodontal disease.
In U.S. Pat. No. 3,723,613, there is disclosed compositions that are capable of diferentially staining "new" and "old" plaque. The compositions are mixtures of dyes such as FDC Red No. 3 and FDC Green No. 3 incorporated into various formulations. In column 3, lines 29-35, it is taught that the dyes in addition to being in the form of a paint may be formulated as a chewable tablet, wafer, powders, lozenges, aerosol and liquid concentrate.
There is no teaching to suggest that such compositions could be incorporated to advantage in a dentrifice.
However, for the benefit of effective plaque disclosure to be fully translated into improved oral hygiene, the removal of this so disclosed plaque must be effective.
In the past, a variety of toothbrushing practices have been taught to be effective in removing plaque. Of necessity, such practices are at best a compromise to take account of the lack of mechanical ability of the individual, the need to effectively clean all surfaces of the teeth whilst at the same time massaging the gums without causing recession. At the same time, variations in an individual's dentition, such as the presence of prosthetic bridges, orthodontic appliances and crossed, crowded or tilted teeth means that a variety of brushing practices may be required to effectively clean all of an individual's teeth.
To meet these difficulties, a number of toothbrush head designs have been proposed and taught to be more effective in the removal of plaque.
Additionally, to overcome the lack of an individual's mechanical ability, electrically driven toothbrushes have been proposed. These are generally claimed to be more effective at plaque removal than the use of manual brushes.
Periodontal probes have been recognized in the prior art. Thus, in U.S. Pat. No. 3,058,225 (Ward) there is disclosed an instrument for automatically obtaining a measurement of attachment levels by means of a probe with a fixed sheath which engages the crown of a tooth when a measurement is made. A slidable needle is moved through the sheath into the periodontal pocket. The distance between the tip of the needle and the end of the sheath, being substantially the periodontal attachment level, is determined electrically by varying the resistance of a resistor in engagement with the needle.
U.S. Pat. No. 3,943,914 (Grenfell et al.) there is disclosed a periodontal probe wherein pocket depth is measured using a stationary needle and a sheath which slides on the needle to the edge of the gingival margin of the pocket when the needle's tip engages the bottom of the pocket. The distance between the end of the sheath and the tip of the needle is converted into an electrical signal to provide an indication of the depth of the periodontal pocket. The electrical signal is recorded on a chart recorder or other means to provide a visual, permanent record.
In U.S. Pat. No. 4,677,756 (Simon et al.) a probe is disclosed comprising a pair of probe elements moveable relative to one another to vary the spacing between sensing areas of each probe, means for producing a signal representing the spacing of said sensing areas, means for monitoring the rate of charge of said signal, and means for recording and/or displaying a value representative of said signal upon the rate of charge of said signal reaching a predetermined value.
It is to be noted that none of these patents in any way control the force at which probing is conducted.
In U.S. Pat. No. 4,340,069 (Yeaple) there is disclosed a probe in which the probing force used to determine pocket depth is predetermined. The probe comprises a magnetizable member mounted within the probe body. A movable lever is also mounted within the body and has a probe tip insertable into a periodontal pocket. The lever has a portion thereof formed from a magnetic material and is further movable between an "engaged" position in which the lever portion is attracted to and engages the member, and a "disengaged" position in which the lever portion is disengaged from the magnetizable member. The probe also comprises means for magnetizing the magnetizable member for releasably holding the lever in its "engaged" position with a preset magnetic force. In this position, the probe is adapted to be inserted into a periodontal pocket and a manual probing force applied thereto when the end of the probe engages the floor of the pocket. When the probing force is increased to the predetermined probing force value, it overcomes the preset magnetic force generated by the magnetizing means causing the lever portion to be moved to its "disengaged" position. The depth of the pocket can then be observed and read on a depth measuring scale on the probe tip for the predetermined probing force.
In PCT/US88/02749 (W089/01314), there is disclosed a periodontal probe system for measurment, storage, and display of periodontal pocket depth, gingival level, and periodontal attachment level of the teeth. The periodontal probe instrument includes an elongate tip with a measurement arrangement that simultaneously measures periodontal pocket depth, gingival level, and periodontal attachment level at each of a plurality of probe sites around a tooth. A pressure sensor in the probe provides a pressure signal indicative of the pressure acting on the tip of the probe. A periodontal measurement is made by inserting the tip of the probe into a gum pocket and gradually increasing the pressure on the probe tip after insertion. At a predetermined pressure leval, the signal processing apparatus samples the depth signals and converts them into measurement signals corresponding to pocket depth and attachment level.
Whilst it would appear that this probe system offers advantages over the prior art, on pages 3 and 4 it is taught that measurement of pocket depth and attachment level are made with reference to the top of the crown of a tooth. This is illustrated in FIG. 2. The difficulty in using the top of the crown as a reference point is that because the crown wears with time, it is not a consistent reference point. In addition, phenomena such as tilting teeth, cusp fracture, restorative procedures and coronal fracture will affect the consistency of the crown as a reference point.
Furthermore, the crowning of a tooth will significantly alter the height of the reference point.
It is therefore evident that this probe system is not adapted to provide a reliable reference point or history of pocket depth development and level of attachments relative to an established permanent reference point.
Because the probe system uses transmission of light to activate light sensitive devices as a measure of pocket depth, any variation in transparency of gum tissue from patient to patient will cause a variation in depth measured. For example, there may be a substantial difference in transparency between the gums of a 5 year old child and the gums of a 65 year old adult. In addition, there are different amounts of melanin and/or keratin in various ethnic, racial and behavioural populations. Thus discrepencies are evident in the density of tissue amongst these groups and even at various sites in the same mouth.
From the foregoing discussion it is evident that all of the prior art probes mentioned are elaborate and sophisticated devices which compromise obvious requirements. Thus, these probes in use would tend to interfere with a dentists need to carefully assess disease pattern and pathology in an effective, practical and economical way.